Make OffscreenCanvas Transferable

third_party/WebKit/Source/bindings/modules/v8/TransferableOffscreenCanvasExtractor.h

Index: third_party/WebKit/Source/bindings/modules/v8/TransferableOffscreenCanvasExtractor.h
diff --git a/third_party/WebKit/Source/bindings/modules/v8/TransferableOffscreenCanvasExtractor.h b/third_party/WebKit/Source/bindings/modules/v8/TransferableOffscreenCanvasExtractor.h
new file mode 100644
index 0000000000000000000000000000000000000000..9afd6e5a3366112d7c209c16ffa33e6e0d62b981
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+++ b/third_party/WebKit/Source/bindings/modules/v8/TransferableOffscreenCanvasExtractor.h
@@ -0,0 +1,37 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef TransferableOffscreenCanvasExtractor_h
+#define TransferableOffscreenCanvasExtractor_h
+
+#include "bindings/core/v8/TransferableExtractor.h"
+#include "bindings/modules/v8/TransferableOffscreenCanvas.h"
+#include "bindings/modules/v8/V8OffscreenCanvas.h"
+#include "modules/ModulesExport.h"
+#include "modules/offscreencanvas/OffscreenCanvas.h"
+
+namespace blink {
+
+class MODULES_EXPORT TransferableOffscreenCanvasExtractor : public TransferableExtractor {
+public:
+    ~TransferableOffscreenCanvasExtractor() override { }
+    bool extract(v8::Local<v8::Value> transferableObject, v8::Isolate* isolate, Transferables& transferables, ExceptionState& exceptionState, const unsigned i) override
+    {
+        if (V8OffscreenCanvas::hasInstance(transferableObject, isolate)) {
+            OffscreenCanvas* offscreenCanvas = V8OffscreenCanvas::toImpl(v8::Local<v8::Object>::Cast(transferableObject));
+            auto& offscreenCanvases = static_cast<TransferableOffscreenCanvas*>(&transferables)->offscreenCanvases;
+            if (offscreenCanvases.contains(offscreenCanvas)) {
+                exceptionState.throwDOMException(DataCloneError, "OffscreenCanvas at index " + String::number(i) + " is a duplicate of an earlier OffscreenCanvas.");
+                return false;
+            }
+            offscreenCanvases.append(offscreenCanvas);
+            return true;
+        }
+        return false;
+    }
+};
+
+} // namespace blink
+
+#endif // TransferableOffscreenCanvasExtractor_h